Coated articles are known in the art for use in window application such as insulating glass (IG) window units, vehicle windows, and/or the like. It is known that in certain instances, it is desirable to heat treat (e.g., thermally temper, heat bend and/or heat strengthen) such coated articles for purposes of tempering, bending, or the like in certain example instances.
In certain situations, designers of coated articles often strive for a combination of high visible transmission, substantially neutral color, low emissivity (or emittance), and low sheet resistance (Rs). High visible transmission for example may permit coated articles to be more desirable in applications such as vehicle windshields or the like, whereas low-emissivity (low-E) and low sheet resistance characteristics permit such coated articles to block significant amounts of IR radiation so as to reduce for example undesirable heating of vehicle or building interiors.
However, heat treatment of coated articles typically requires use of temperature(s) of at least 580 degrees C., more preferably of at least about 600 degrees C. and still more preferably of at least 620 degrees C. The use of such high temperatures (e.g., for 5-10 minutes or more) often causes coatings to break down and/or causes one or more of the aforesaid desirable characteristics to significantly deteriorate in an undesirable manner. Those in the art strive for heat treatability in certain applications, coupled with acceptable optical and solar characteristics.
U.S. Pat. No. 6,686,050 (see also US 2002/0064662 A1) discloses, inter alia, a heat treatable coated article. Consider the below-listed layer stack where the layers are listed in order from a 2.1 mm glass substrate outwardly. The thicknesses are provided for purposes of example only.
Glass SubstrateThickness (Å)TiO2140Si3N4160NiCrOx32Ag96NiCrOx26SnO2730Si3N4160NiCrOx21Ag101NiCrOx26SnO2128Si3N4370
As evidenced by Examples 1-3 of U.S. Pat. No. 6,686,050, following heat treatment coated articles with these layers had sheet resistance (Rs) of about 3.3 to 3.5 ohms/square, and following lamination had a visible transmission of about 75%. There is certainly room for improvement as to one or both of these respects. For example, it would be desirable if: (a) visible transmission could be increased following lamination so as to improve optical characteristics, and/or (b) sheet resistance lowered before and/or after heat treatment (HT) so as to improve solar characteristics.
In view of the above, it will be apparent to those skilled in the art that there exists a need for coated articles which are capable of providing high visible transmission, substantially neutral color, low emissivity (or emittance), and/or low sheet resistance (Rs). In certain example embodiments, it may be desired that one or all of these characteristics can be achieved even after the coated article has been heat treated and/or laminated.